Field
Example aspects described herein relate generally to optical communication networks, and, more particularly, to methods, apparatuses, systems, and computer programs for providing protection for optical communication network channel connections.
Description of the Related Art
Network failures, such as fiber cuts, network element failures, and/or failures or defects of one or more individual optical channels (i.e., wavelengths), can have a great impact on networks and can often cause decreased network availability for a large portion of a network. Various techniques have been used to provide protection of optical network connections through the use of redundant or backup communication paths, on a per-fiber basis or a per-channel basis.
One conventional technique for protecting a wavelength division multiplexed (WDM) optical network signal employs an optical channel monitor (OCM) and a WDM switch in a network element. The OCM sweeps through each channel of the WDM signal and provides an optical power level measurement for each channel. Then, based on the power level measurements provided by the OCM, the WDM switch routes the entire WDM signal, including all its constituent channel signals, through either a working path or a protection path. For example, if the power level measurement for the working path is lower than the power level measurement for the protection path (e.g., owing to a failure or defect affecting the working path), then the WDM switch may route the WDM signal through the protection path.
One advantage of employing an OCM and a WDM switch to provide network protection is that multiple optical channels included in a WDM signal may be protected by using a single OCM. However, because this technique employs WDM switches, this technique does not enable separate switching (and thus separate protection) of individual optical channels. Also, because this technique reserves entire fibers as protection paths instead of individual channels, it can be impractical to use this technique to protect mesh networks, which typically include a large number of fibers and channels. Additionally, because of the considerable time it can take for an OCM to successively measure power levels for each channel, OCMs often do not enable detection of signal defects at a rate sufficiently high to enable fast switching times, such as those that may be demanded for certain types of high-priority network traffic (e.g., digital telephone traffic).
A conventional technique for protecting an individual channel optical network signal employs, in a network element, an optical protection switching module (OPSM) including a photodetector. The photodetector provides an optical power level measurement for the signal. Then, based on the power level measurement provided by the photodetector, the OPSM routes the signal through either a working path or a protection path.
One advantage of employing an OPSM and a photodetector to provide network protection is that the photodetector can often detect signal defects at a rate sufficiently high to enable fast switching times demanded for some network traffic. However, since an individual OPSM including a photodetector is needed for each channel, the use of OPSMs and photodetectors to protect optical network connections can become quite costly as the number of optical channels increases.